October 1994
DP84910 (-36/-50)
Integrated Read Channel
General Description
The DP84910 integrates most functions of the hard disk
read channel electronics onto a single 5V chip. It incorpo-
rates a pulse/servo detector, a programmable integrated
channel filter, a data synchronizer, a frequency synthesizer,
and a serial port interface. The chip receives data from a
read preamplifier, filters and peak detects the read pulses
for both data and embedded servo information and resyn-
chronizes the data with the system clock.
Independent power down control for all of the major blocks
within the chip is provided via three bits in the control
register
(SYNC PWR DN,
STH PWR DN
and
PD PWR DN) to manage power consumption. In addi-
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tion, two pins (SLEEP and IDLE/SERVO) are available to
control power management. The sleep mode pin (SLEEP)
powers down all circuitry on the chip including the control
register. In this mode the maximum power supply current is
2 mA; the control register data must be reentered when
exiting this mode. The idle/servo mode pin (IDLE/SERVO)
toggles the device between the idle and servo modes. In the
idle mode, only the control register and pulse detector bias-
ing circuitry necessary for a quick recovery are active. In the
servo mode, the pulse detector portions needed for servo
detection are active as well as the control register. Less
than 15 ms is required for the pulse detector to recover from
the idle condition. The control register data is not lost when
The DP84910 is available in two versions, DP84910VHG-36
and DP84910VHG-50. The DP84910VHG-36 is specified to
operate over
a data rate range of 7.5 Mbits/sec to
36 Mbits/sec. The other version, DP84910VHG-50, will op-
erate over a data rate range of 13.7 Mbits/sec to 50 Mbits/
sec.
This device is specifically designed to address zoned data
rate applications. A channel filter with control register se-
lectable cutoff frequency and equalization is provided on-
chip. This eliminates the need for multiple external channel
filters and allows for greater flexibility in the selection of
zone frequencies. The frequency synthesizer provides cen-
ter frequency information for the data synchronizer and a
variable frequency write clock. There is no need for any off-
chip frequency setting components or DACs.
k
this pin is toggled. The pin can be rapidly toggled ( 15 ms)
to achieve average power consumption savings and will
keep the read/write head on track. Seventeen power and
ground pins are provided to isolate major functional blocks
and allow for independent supply voltage filtering, thus en-
hancing noise immunity.
(Continued)
A four-bank control register is included to control zoning
operations and configure general chip functions. At V
CC
power-up the chip self-configures by presetting all bits in the
control register to predetermined operating setup condi-
tions.
TL/F/11777–1
FIGURE 1. DP84910 in a Typical Disk Drive System
MICROWIRETM is a trademark of National Semiconductor Corporation.
C
1996 National Semiconductor Corporation
TL/F/11777
RRD-B30M116/Printed in U. S. A.
http://www.national.com